Combination coking and catalytic cracking process



Feb. 9, 1943.

'A J. K ROBERTS COMBINATION COKING AND CATALYTIC CRACKING PROCESS Filed May 27, 1938 NN NN.

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m o 52@ Nh T INVENTOR s ,0h K. Ro fs ATTORNEY lPatented Feb. 9, 194.13 y

COMBINATION colmar;r AND camu/Tic caAcxING PnocEss .Joseph K. Roberts, Flossmum, 111., assignmto A Standard Oil Company, Chicago, Ill., a corporation of Indiana Appiieauon May 27. 193s, serai No. 210,316

(ci. 19e-49) `11 Claims.

This invention relates to a. combination coking andl catalytic cracking process, and it pertains more particularly to an improved method for the manufacture of high quality motor fuels from petroleum and petroleum products.

An object of the invention is to obtain maximum yields of high quality motor fuel from petroleum olis, including oils derived from shale, coal, lignite and other carbonaceous materials and products thereof. More particularly, thev object is to produce a motor fuel characterized by a high octane number-a fuel which will have a minimum tendency to knock when used in high compression spark ignition internal combustion engines. A further object is to produce such a fuel which is free from corrosive sulfur and which may be easily stabilized against oxidation and gum formation, which will have a high blending value and a good lead tetraethyl response, and, in short, which will meet all of the rigid yspecifications for a high quality motor fuel.

A further object of the 'invention is to provide a new and improved method` and means for combining a thermal coking process with a catalytic conversion process, whereby each process may be operated' with maximum effectiveness and eiciency.v A further object is to remove coke-forming materials from charging stock to a catalytic cracking process so that the catalyst may be operated for a longer period of time or for the production of larger yields of gasoline before necessary shutdowns for regeneration.

A further object is to subject "dirty (cokeforming) components of charging stock from the fresh feed to a coke furnace in combination with low gravity 'residues from the coking and/or cracking processes, so that maximum gasoline yields may be obtained from such stocks. A

further object is to subsequently treat the liquidy most eflectivelyutilized for v'the production of maximum yieldsv of high quality gasoline. Other objects will be apparent as the detailed descrip- Aist tion of the invention proceeds.

Gasolines and gas oils produced by coking Arepresented by aluminum silico fa preferred modification of the improved process.

operations are usually more paraillnic (and hence are characterized by lower knock ratings or octane numbers) than those of gasolines and gas oils produced by high pressure thermal cracking systems. introduce the products from the coking drums at a temperature of about 750 to 900 F.,'pref erably about 825 F., into a flash drum into which I also introduce a fresh feed. which has been preheated to a temperature of incipient cracking, l. e.. about 700 to 800 F. The coking drum products supply additional heat to the introduced feed and thegases from the coking drum help to strip out the gasoline and light gas oil fractions from the liquids in theash drum so -that substantially all of the lighty gas oil is separated from the heavy residual products. These heavy residual products are returned to the coking operation; and the light gas oil. either with or Without the naphtha fraction, is heated to about 850 to l000 F., preferably about 925 F. to 950 F.

and passed through a catalytic cracking chamber. This catalytic cracking step converts the mixture of fresh feed, light gas oil and coking drum light gas oil'either with or Without the naphtha from both sources into high quality motor fuel which is characterized by a specially high octane number. The products of the catalytic cracking are then fractionated, the gasoline fraction is stabilized and the cycle stock is either returned to the flash drum or directly Ito Athe coking furnace.

As catalysts for my process I may employ acid-treated bentonite, or other activated hydrosilicate of alumina, particularly .combinations in which the ratio of silica to alumina is about 4:1.

VThe catalyst may be prepared .by depositing alumina or oxides of other metals such as copper,

cadmium, cerium, nickel, boron, etc. on silica.

gel. I may also employ catalysts of the type fluoride,

Ah(SiFa)a. I may use metal oxide catalysts on of the so-called homogeneous type, as exemplified by butyl bromide and other alkyl halides, either alone or in combination with the heterogeneous catalysts hereinabovereferred to.

The invention will be more clearly understood from the following detailed description, and from the accompanying drawing which forms a part of. this specification and in which I have shown The invention is applicable to the production of high quality motor fuell from all types of min- In practicing my invention I I a ow diagram of manhole 25".

As catalyst material I may employ any known cracking catalysts, of which there are a large number. Activated hydrosilicate of alumina has also applicable to slop refinery cuts, gas oils (particularly cycle or dirty gas oils), naphtha or mixtures of some or any of the stocks which are commonly produced in petroleum refineries.

'I'he fresh feed is introduced by pump lo through line II and preheating coils I2 of pipe still I3, thence through line I4 to flash drum I5. The oil is preferably heated in coils I 2 to incipient cracking, i. e., to a temperature of about '100 to 800 F. It should be understood that any suitable'type of preheater may be employed forthis purpose, and that the temperature of preheating will depend-upon the particular stock charged and the heat balance of the unit.

The flash drum is preferably operated at about 50 to 100 pounds per square inch, and it is provided with conventional baille plates or bubble plates. The temperature conditions in this drum are maintained to effect the separation of light gas oil, naphtha, gasoline and gases from heavy gas oil and residue, the latter being withdrawn from the base of the drum through line` IB-and forced by pump I'I through coils I8 of coking furnace I9, the oil being discharged through line 20 and one of the branched lines 2|, 2I and 2|" 1 perature of the vapors introduced through line 24 may vary from about 750 to 900 F., but this temperature is usually about 825 to 850 F. When materials in coking drum 22 are substantially reduced to coke this drum is cut out of the system and oil is introduced through line 2|' to coking drum 22'. While the coke is cooling in drum 22, the coke in drum 22" is being withdrawn through The operation of these so-called "delayed cokers is well-known in the art and furtherdetailed description is therefore unnecessary.

The hot vapors returned through line 24 to flash drum I are partially condensed by the incoming feed stock and simultaneously these gases and vapors tend to effect the vapor-ization and stripping of light gas oilfrom the incoming 'feed stock. The entire mixture of light gas oil, gasoline and gases may be withdrawn from the top of nash drum I5 through line 2B, passed through radiant or roof coils. 21 of pipe still I3 to increase their temperature to about 850 to 1000" F., and then introduced through line 2l and one of the branched linesr29, 29' or 28" into catalyst chamber 30, 20' or 20". These catalyst chambers may be of any conventional type and may be diagrammatically represented as vertical drums conbeen found to give excellent resultsparticularly when the ratio of silica to alumina is about 4:1. Such catalyst may be made from acid-treated bentonite by making a dough of such bentonite and water, forming pellets about 1A; to 13s of an inchrin diameter and thoroughly drying said pellets, preferably at temperatures of about 850 to 1000 F. I may, however, deposit alumina or other metal oxides on silica gel, i. e. sodium silicate may be precipitated with hydrochloric acid and washed free from chlorides and may then be impregnated with a solution of copper, cadmium or cerium sulfates or nitrates, nickel chloride, boric acid or other solutions of metal salts or acids, the catalyst being then thoroughly dried. Aluminum iluosilicate offers the advantage of relatively small carbon deposits. Butyl bromide or other alkyl halides or halogen acids may be used as promoters or homogeneous catalysts. either alone or in commotion with the heterogeneous catalysts hereinabove described.

Vapors from line 28 are preferably passed through the catalyst chamber at a space velocity ofh about 0.25 to 2.0 volume of liquid feed per vol.

umef catalyst space per hour. For light gas oils the preferred temperature is about 925 F., although higher temperatures may be used, particularly with higher space velocities. For lighter stock such as naphthas, the .temperature should preferably be about 1000 F. The optimum temperature for any given stock may be determined by a few simple preliminary experiments.

The catalyst chambers, like the coking drums, are operated in sequence, one or more chambers -being revivified while another chamber is on stream. The revivification may be effected by controlled oxidation with hot flue gases contain-` needs no further detailed description.

` of fractionating tower 39. This tower is provided taining beds of catalyst li supported on suitable trays 32. It should be understood, however, that' rial. No novelty is claimed in the particular catalyst chamber and it will therefore not be described in further detail'.

with a suitable heating means at its base such as a steam coil or an external heater 40 through which the bottoms are circulated. Vapors from the top of the fractionating tower are withdrawn through line 42 and partial condenser 42 to separator 44 from whichV gases are withdrawn through line 45, a part. of the liquids are returned as reflux through line 4l and the remaining liquid is withdrawn through line 4T to a stabilizer tower 4l, or thru line 49 for further processing or nishing. The tower may-be operated under conditions to withdraw heavy naphtha from side stream 5l for further processing. Stabilizer 4l is provided with suitable heating means at its base and reflux means at its top and may, in fact, be

' of conventional design. propane and lighterases being withdrawn from the top thereof and stabase through line` I The cracked cycle stock from the base of fractionating tower 38 may be withdrawn through line 52 and line 53 to line I 6 for admlxture with residue enroute from the base of flash drum Il to the coking furnace (altho coking is not as desirable as cracking on stocks boilingbelow 800 F.). Alternatively, it may be introduced through line 54 to line I4 entering the flash drum, or through line 55 to line I0 for admixture with fresh feed. I have found that this cracked.

than catalytic cracking for obtaining high gasoy line yield from this particular stock.

The cracked and stabilized gasoline from line 5| may have an octane number of about 80 to 90, and is characterized by a very low sulfur content. It requires only a very light treating, isv

easily sweetened and may be effectively stabilized with a very small amount of antioxidant. It is an excellent blending fuel, and shows an excellent response to lead tetraethyl for further increase of octane number.

From the above description it will be seen that the fresh feed is practically all converted Into cracked gasoline, coke and gases, the-gasoline yield being in some cases as high as 76% ony crude and 50% on reduced crude (from which 400 F. end point products have been removed). The gases may be polymerized to form still further quantities of high quality gasoline in a convenv tional polymerization system; or may be reacted with liquid hydrocarbons in a gas reversion process.

While I have described the passage of all of the gases and vapors from flash drum l5 through the catalytic conversion system, it should be understood that suitable bubble'trays or other fractlonating means may be employed'in the top of ilash drum I5 or in addition to flash drum I5 (such as a separate fractionating tower, not shown), so that selected fractions from the ash `drum are separately passed through the catalytic craicking system. For instance, C4 and lighter hydrocarbons may be withdrawn from the top of the flash drum (or other fractionator) through line 5l to a conventional polymerization or gas reversionsystem, and the mixture of gasoline and light gas oil may be withdrawn as a side stream through line 58 and forced by pump B9 through heating coil 21 and thence to the catalytic conversion system. Alternatively, the light naphtha and gases may be withdrawn through line 51 and only the heavy naphtha and I rating naphthas and gas oils 'from the fresh feed Y vfundar: -bmzea manne being withdrawn fromme andfrom the coking ldrums are catalyticallyconverted into motor fuels of high quality and par-V ticularly .of high octane number.

While I have described in detaily a preferred 5 embodiment of my invention, it should be understood that I do not limit myself to sluc'h details except as denned by the following claims, which should be construed as broadly as the prior art will permit. l

10 I claim:

1. The method of converting heavy hydrocarbons into high quality motor fu'el, which comprises heating said hydrocarbons to incipient cracking and introducing said heated hydrocarbons into a flash zone, withdrawing hydrocarbons heavier than light gas oil from the base of said flash zone, heating the withdrawn hydrocarbons heavier than` iight gas oil to about 900 -to 950 F.

and introducing them into a coking zone, intro- Y' ducing gases and vapors from said coking zone into said flash zone for combination with the introduced fresh feed, and catalytically cracking the light gas oil fraction of the hydrocarbons withdrawn from the upper part of said flash zone to produce a motor fuel of high octane number.

4 2. The method of claim 1 wherein the catalytic cracking is effected at a .temperature of about 850 to 1000 F.

3. 'I'he method ofclaim 1 wherein the catalytic cracking. is effected in the presence of a catalyst comprising silica and a metal oxide.

4. The method of converting heavy hydrocarbons into high quality motor fuel. which comprises introducing said hydrocarbons into a flash y zone, continuously withdrawing hydrocarbons heavier than light gas oil from the base of said flash zone, increasing the pressure on the withdrawn hydrocarbons and introducing them into a coking drum at a temperaturelof about 900 to 950 F. whereby lsaid hydrocarbons undergo decomposition to form coke,l gases and vapors introducing the gas and vapors produced by the coking process into said ash zone for admixture with incoming fresh feed, withdrawing Vlight gas oil, vnaphtha and gases from the upper part of said flash zone and catalytically cracking said light gas oil to produce high quality motor fuel of high octane number. r

5. 'I'he method of claim 4 Whereinthe light gas the presence of naphtha from the flash zone.

6.'The method of claim 4 which includes the further steps of fractionating products of the catalytic cracking into gases. gasoline and cracked cycle stock, recycling said cracked cycle stock to the coking tion. l

7. The process of converting heavy hydrocarbons into high quality motor fuel which comprises preheating said hydrocarbons to a temperature below cracking temperature, introducing said preheated hydrocarbons into a flash zone, withdrawing liquids heavier than light gas oil from the base of said flash zone, heating said withdrawn liquids to a temperature of about 900 to 950 F., coking said heated liquids under a pressure of about 50 to 100pounds per square inch to form coke and light hydrocarbon gases and vapors, returning said light hydrocarbon gases and vapors at a temperature of about 750 to` 900 F., to said .flash drum, maintaining said flash drum at substantially the same pressure as the pressure in the coking drum, withdrawing light gas oil from the upper part of said ash drum, heating vsaid light gas oil to a temperature oil from the flash zone is catalytically cracked in step and stabilizingthe gasoline frac- M a fraction heavier than gasoline, and gases respectively.

8. The method of claim 7 wherein naphtha is passed together with the light gas oil from the top of the ash zone through the heating step, catalytic conversion step and iinal fractionation step.

9. The method of claim 7 wherein the fractionated product heavier than gasoline is recycled to the coking step. l A

10. Thev method of claim 7 wherein the fraction heavier than gasoline is recycled to the coking step by Way of the ash zone.

, .11. In a process of catalytic cracking wherein liquid hydrocarbons are contacted with a nonoxidizing cracking catalyst of the silica alumina type at a temperature of about 850 to 1000 F. and wherein a carbonaceous deposit 'accumulates on the catalyst so that the catalyst requires periodic regeneration for removal of such deposits, the method of prolonging the activity of the catalyst and decreasing the frequency of required regeneration, which method comprises introducing charging stock into a ash zone, pumping heavy hydrocarbons including heavy gas oil from the base of said flash zone through a heating zone and heating said heavy hydrocarbons to a temperature of 900 to 950 F., introducing the heavy hydrocarbons at a temperature of 900 to Y950" F. into a coking zone maintained at such temperatures that the introduced materials are converted into coke, gases and vapors, returning said gases and vapors from said coking zone to said iiash zone, withdrawing light gas oil and lighter hydrocarbons from the upper part of said iiash zone, and charging the light gas oil which is withdrawn from the upper part of said flash zone to said catalytic cracking process.

JOSEPH K. ROBERTS. 

